The results of the Iowa caucuses illuminate the basic structure of today’s Republican Party and offer clues about what’s to come between now and the end of January.

Pew’s “political typology,”the latest iteration of which appeared last May, provides the best point of departure. That report used a statistical technique known as cluster analysis to identify four major pro-Republican groups: Staunch Conservatives (11 percent of registered voters), Main Street Conservatives (14 percent), Libertarians (10 percent), and “Disaffecteds” (11 percent). The Iowa entrance polls showed that Staunch Conservatives—the sorts of people most likely to identify with the Tea Party—preferred Santorum to any other candidate; Main Street Conservatives, who may be anything from Rotarians to country-clubbers, went for Romney; and of course Libertarians found a stalwart champion in Ron Paul.

But who are the Disaffecteds? According to Pew, they are both anti-government and anti-big business. They are social conservatives with a deep antipathy to illegal immigration. But they are also the most financially insecure of all the groups—among Democrats and Independents as well as Republicans—and perhaps for that reason, less averse to a government that extends a helping hand to the downtrodden. For the most part, they are whites with no more than a high school education. Many report personal or family struggles with unemployment.

The Disaffecteds are, in short, the kinds of blue-collar workers who became untethered from the Democratic Party during the 1970s and found a new, not wholly comfortable home among Republicans. While they form a relatively small share of the Iowa Republican electorate, Pennsylvania is full of them, as are industrial states throughout the Midwest, and Santorum did reasonably well with them in his two successful races for the Senate. They are not the kinds of people who tend to identify with the Mitt Romneys of this world.